I thought the sergeant was further than he really was because of the font - he was above me by a couple of spaces and I decided to just wing it.
But...aren't all of the floor tiles dots? That alone should give you the relative measurement tool necessary to judge distance: even if the spacing is different, the grid is all but given. But hell, if you have a problem reading it without really thinking about it then I'm not here to judge.
If you're running from Windows, you can just go to the Command Prompt properties and change you font via the Font tab. For me, I have Consolas and Lucida Console in additional to the default that is Raster Fonts. If neither of those appeal to you (or don't show up), you can
edit fonts in yourself. Just keep in mind that you'll need a fixed width font for it to look any good.
That aside, I don't know any particularly squarish fonts offhand. X@COM actually uses a spritesheet for its fonts, whereas the current version of DoomRL is literally played in a console (not unlike Rogue itself), so it's not the fairest comparison.